In a conventional high-precision, high-resolution (reading precision of 1 mg or less) electronic balance, external air currents have a substantial effect on the weighing precision, so a method of enclosing the vicinity of the scale pan with a windproof case is employed in order to eliminate such causes of error. FIG. 7 is a top view (A) and a side view (B) showing an example of the external appearance of an electronic balance with a windproof case. As shown in the drawings, in an electronic balance 101, a windproof case 105 is disposed on a main body case 104 comprising a lower case 102 which typically houses electrical circuits for measuring the weights of samples and a display part for displaying weighed values and an upper case 103 which is mounted on top of the lower case 102 (see Patent Literature 1, for example).
The windproof case 105 comprises a pair of L-shaped frames 106A and 106B erected on the upper case 103, a tube structure 107 erected on the rear part, a frame 109 comprising a four-sided frame which makes contact with the upper parts of the L-shaped frames 106A and 106B and is fastened to the upper part of the tube structure 107 with screws, a front glass 110 disposed on the front surface of the frame 109, an upper slide glass 111 which can be moved forward or backward when inserting or removing an object to be weighed, a right slide glass 112, and a left slide glass 113 so as to enclose a scale pan 114 in an airtight state.
Patent literature 1) Japanese Unexamined Patent Application 2001-99699